Littmann



Feb. 2, 1965 D. LITTMANN 3,168,161

STETHOSCOPE Filed Sept. 9, 1963 INVENTOR.

DAVID L! TTMAN ATTORNEYS United States Patent 3,168,161 STETHOSCOPE David Littmann, Belmont, Mass., assignor to Cardiosonics Medical Instruments Corporation, Belmont, Mass., a corporation of Massachusetts Filed Sept. 9, 1963, Scr. No. 307,739 7 Claims. (Cl. 181--24) This is a continuation in part of application Serial No. 138,440 filed Sept. 15, 1961, now abandoned.

The present invention relates to a stethoscope and more particularly to an improved means for connecting the ear tubes to the sound tube of a stethoscope.

Convention'ally, stethoscopes have a pair of rigid ear tubes interconnected by the arms of a flexible Y member and with the stern of the Y in turn connected to the head of the stethoscope. In such constructions an external spring arrangement spring tensions the ear tubes towards one another so that they may grip the wearers head. Such a, construction however has proved to be cumbersome and bulky and in addition is relatively expensive.

Several modifications of this design have been attempted in which the spring member is integrally formed with the Y shaped interconnected sound tube. Such structures are represented by Morin Patent No. 1,585,407, issued May 18, 1926. These constructions however have not been satisfactory for several reasons.

One difficulty with such modifications is that the leaf spring arrangement heretofore used does not have sufficient strength to withstand continued flexing particularly at the junction of the spring and ear tubes. In addition a single leaf spring does not satisfactorily angularly index one ear tube with respect to the other so that its ends will assume a proper position to engage the wearers ear. As a result of these difiiculties devices heretofore made of the type referred to are quite susceptible to fatigue fractures at the weakest point of the spring, namely the crease line or junction of the flanges and the main body of the spring where bending most naturally takes place, and further do not satisfactorily hold the stethoscope in place when in use.

The present invention is designed to overcome such problems and provides a construction of sufficient strength to withstand radial torques and longitudinal pulls and thrusts. In stethoscopes made in accordance with the present invention, the ear tubes are secured in selected angular relationship to one another by a pair of leaf springs so as to properly engage the wearers cars at all times. In addition, these stethoscopes will not readily break, particularly at the ends of the leaf springs contained within the Y shaped sound tube. Furthermore the present stethoscope can be collapsed to a much more compact structure than can devices made in accordance with earlier known art.

In the present invention there is provided a stethoscope having a pair of rigid ear tubes and a flexible Y shaped sound tube providing two arms and a stem with one ear tube extending outwardly from each of the arms. A pair of leaf springs are contained within the arms of the Y shaped sound tube and extend past the stern into each arm. These springs are substantially coextensive with one another and are secured in facing relationship at their ends to the ends of the ear tubes. One leaf spring is rigidly interengaged and the other leaf spring is slida'bly interengaged at their ends to the ear tubes. Helical coils are wrapped about narrowed diameters of the ends of each ear tube and the corresponding ends of the leaf springs to secure the leaf springs in a manner previously set forth to the ends of the ear tubes. The narrowed diameter ends of the ear tubes are preferably formed of semicylindrical sections having a diameter less than the main portion of 3,168,161 Patented Feb. 2., 1965 'ice the ear tubes and with opposed longitudinal edges which engage one of the leaf springs in facing relationship.

These and other objects and advantages of the present invention will be more clearly understood when considered in connection with the accompanying drawings in which:

FIG. 1 is a cross sectional elevation of the stethoscope showing the lower portion or stem of the Y shaped sound tube broken away and without the stethoscope head;

FIG. 2 is an enlarged perspective detail of the interengaged leaf spring and the adjacent end of an ear tube; and

FIGURE 3 is a perspective fragmentary exploded view of the end of an ear tube and the leaf springs secured thereto.

As illustrated in the drawings a pair of stethoscope ear tubes and 11 of conventional shape are provided with ear plugs 12 and 13 respectively at their outer ends. The inner ends of these ear tubes 10 and 11 extend into the Y shaped sound tube 14 having arms 15 and 16 and stem 17, the stem 17 being connected by suitable means to a conventional stethoscope head (not shown). The Y shaped sound tube 14 is made preferably of a synthetic resin material such as disclosed in my copending application Serial No. 36,641, filed June 16, 1960, now Pat. No. 3,108,652.

The ends of each of the ear tubes 10 and 11 may be identically formed as illustrated in FIG. 3. As illustrated, the end portion is formed with a reduced diameter. A section of the end portion is milled out partially along its length to form a semicylindrical member having op posed longitudinal edges 19 and 20. The edges 19, 20 terminate short of the inner end of reduced end portion 18. A pair of dog cars 21 and 22 project from each of these longitudinal edges 19 and 20 at a distance spaced from the ends of the edges. Preferably these dog ears 21, 22 are spaced closer to the main portion of the ear tube than into the end of the tube. The outer end of the reduced portion 18 is beveled as illustrated in FIG. 2 at 26. The leaf springs 27 and 28 are each formed of parallel strips of spring steel of uniform width throughout their entire length. Preferably strip 27 which forms an outer strip is slightly wider than the inner strip. In a typical construction the outer strip or spring 27 is wide, while spring 28 is /8 wide. These springs are preferably formd by the best spring steel available and are rolled and formed with rounded edges to avoid damaging the Y shaped sound tube. Outer spring 27 is formed with a pair of notches 30, 31 corresponding in size and shape and adapted to engage dog cars 21, 22. The springs 27 and 28 are secured in facing relation at their ends to the opposed edges 19, 20 of the semicylindrical end section of the ear tubes by a helical coil 35. This helical coil extends from the inner end of the reduced diameter end portion almost but not quite the length of the sernicylindrical end portion of the ear tubes, leaving a section 36 (FIG. 2) exposed beyond the end of the coil. The coil extends beyond the end of edges 19, 20 and the springs 27, 28 at the inner end of the end portion. This arrangement also normally provides a very small but definite space indicated at 39 between the very end of the ear tubes and the outer surface of the leaf spring 27. These springs 27 and 28 are spaced apart at their center portion indicated at 40 in FIG. 1. This arrangement securely locks the outer leaf spring 27 to the ear tube but may allow the leaf spring 28 a degree of freedom to slide longitudinally when the ear tubes 10 and 11 are flexed with respect to one another.

The construction described above provides a simple means of indexing the ear tubes with respect to one another and therefore provides a simple means of securing the ends of the ear tubes in a desired angle one to another, so that they will properly fit the wearers head. This may be accomplished by a simple milling fixture during the manufacturing process.

In addition to the advantages heretofore set forth, the helical coil securing the springs to the ear tubes compensates for accidental side thrusts or forces and thereby minimizes the likelihood of a fracture at the junction of the ear tubes and springs when a force is applied in the wrong direction.

Although the present invention in its preferred form contemplates providing notches in the outer spring 27 as illustrated at 30 and 31, the invention also contemplates securing of the springs 27 and 28 to the ear tubes without the use of notches or corresponding dog ears. The invention also contemplates the utilization of notches in the inner spring 28 which may be formed with a greater diameter than the outer spring 27. This latter construction may provide a stronger construction of the tube and spring inte-rengagement because less wall of the tube need be milled out. In such structures the leafs may not slide relative to one another at their ends.

Having now described my invention, I claim:

1. In a stethoscope construction having a pair of rigid elongated ear tubes and a flexible Y tube with integral arms and a stem, a pair of elongated leaf springs positioned within said Y tube arms and prestressed to form U-shaped arcs, and means interengaging each of said leaf springs at their ends to said ear tubes with one spring longitudinally slidable with respect to the other to secure said ear tubes in selected angular relationship to one another.

2. In a stethoscope construction having a pair of rigid elongated ear tubes and a flexible Y tube with integral arms and a stern, a pair of fiat elongated leaf springs of uniform width along substantially their entire length positioned within said Y tube arms and prestressed to form U-shaped arcs, and means interengaging each of said leaf springs at their ends to the ends of said ear tubes with one spring rigidly engaged by said ear tubes and the other 4 spring longitudinally slidable at its ends with respect to the other.

3. A stethoscope construction as set forth in claim 2 wherein said elongated leaf springs are spaced apart at their centers and converge towards one another at their ends.

4. A stethoscope construction as set forth in claim 3 wherein said springs terminate short of the ends of said arms and resiliently support said arms in substantially a U-shaped configuration.

5. In a stethoscope construction having a pair of rigid elongated ear tubes and a flexible Y tube with integral arms and a stem, a pair of elongated leaf springs positioned within said Y tube arms and prestressed to form U-shaped arcs, and means interengaging each of said leaf springs at their ends to said ear tubes to secure said ear tubes in selected angular relationship to one another.

6. In a stethoscope construction having a pair of rigid elongated ear tubes and a flexible Y-tube with integral arms and a stem, a pair of elongated leaf springs positioned within said Y-tube arms and prestressed to form U-shapcd arcs, and means interengaging each of said leaf springs at their ends to said ear tubes comprising a pair of means with each means wrapped about and enclosing portions of adjacent ends of said leaf springs and an end of one of said tubes.

7. A stethoscope construction as set forth in claim 6 wherein said means enclosing portions of said leaf spring ends include a coil means Wrapped about said ends and the ends of said tubes.

References Cited in the file of this patent UNITED STATES PATENTS 882,700 Lewis Mar. 24, 1908 1,585,407 Morin May 18, 1926 1,651,531 Martus et a1. Dec. 6, 1927 2,075,196 Hand Mar. 30, 1937 

1. IN A STETHOSCOPE CONSTRUCTION HAVING A PAIR OF RIGID ELONGATED EAR TUBES AND A FLEXIBLE Y TUBE WITH INTEGRAL ARMS AN A STEM, A PAIR OF ELONGATED LEAF SPRINGS POSITIONED WITHIN SAID Y TUBE ARMS AND PRESTRESSED TO FORM U-SHAPED ARCS, AND MEANS INTERENGAGING EACH OF SAID LEAF SPRINGS AT THEIR ENDS TO SAID EAR TUBES WITH ONE SPRING LONGITUDINALLY SLIDABLE WITH RESPECT TO THE OTHER TO SECURE SAID EAR TUBES IN SELECTED ANGULAR RELATIONSHIP TO ONE ANOTHER. 